<!DOCTYPE html>
<html>
<head>
  <style>
    div#x::first-letter { color: blue; }
  </style>
</head>
<body>
<div id="x">x</div>
<script>
  document.body.offsetWidth;
  var div = document.getElementById("x");
  div.id = "y";
  div.removeChild(div.firstChild);
</script>
</body>
</html>
